agg_span_image_filter_rgb.h

//----------------------------------------------------------------------------
// Anti-Grain Geometry - Version 2.4
// Copyright (C) 2002-2005 Maxim Shemanarev (http://www.antigrain.com)
//
// Permission to copy, use, modify, sell and distribute this software 
// is granted provided this copyright notice appears in all copies. 
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//
//----------------------------------------------------------------------------
// Contact: mcseem@antigrain.com
//          mcseemagg@yahoo.com
//          http://www.antigrain.com
//----------------------------------------------------------------------------
//
// Adaptation for high precision colors has been sponsored by 
// Liberty Technology Systems, Inc., visit http://lib-sys.com
//
// Liberty Technology Systems, Inc. is the provider of
// PostScript and PDF technology for software developers.
// 
//----------------------------------------------------------------------------
#ifndef AGG_SPAN_IMAGE_FILTER_RGB_INCLUDED
#define AGG_SPAN_IMAGE_FILTER_RGB_INCLUDED

#include "agg_basics.h"
#include "agg_color_rgba.h"
#include "agg_span_image_filter.h"


namespace agg
{

    //===============================================span_image_filter_rgb_nn
    template<class Source, class Interpolator> 
    class span_image_filter_rgb_nn : 
    public span_image_filter<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_filter<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::calc_type calc_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask
        };

        //--------------------------------------------------------------------
        span_image_filter_rgb_nn() {}
        span_image_filter_rgb_nn(source_type& src, 
                                 interpolator_type& inter) :
            base_type(src, inter, 0) 
        {}

        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);
            do
            {
                base_type::interpolator().coordinates(&x, &y);
                const value_type* fg_ptr = (const value_type*)
                    base_type::source().span(x >> image_subpixel_shift, 
                                             y >> image_subpixel_shift, 
                                             1);
                span->r = fg_ptr[order_type::R];
                span->g = fg_ptr[order_type::G];
                span->b = fg_ptr[order_type::B];
                span->a = base_mask;
                ++span;
                ++base_type::interpolator();

            } while(--len);
        }
    };



    //==========================================span_image_filter_rgb_bilinear
    template<class Source, class Interpolator> 
    class span_image_filter_rgb_bilinear : 
    public span_image_filter<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_filter<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::calc_type calc_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask
        };

        //--------------------------------------------------------------------
        span_image_filter_rgb_bilinear() {}
        span_image_filter_rgb_bilinear(source_type& src, 
                                       interpolator_type& inter) :
            base_type(src, inter, 0) 
        {}


        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);
            calc_type fg[3];
            const value_type *fg_ptr;
            do
            {
                int x_hr;
                int y_hr;

                base_type::interpolator().coordinates(&x_hr, &y_hr);

                x_hr -= base_type::filter_dx_int();
                y_hr -= base_type::filter_dy_int();

                int x_lr = x_hr >> image_subpixel_shift;
                int y_lr = y_hr >> image_subpixel_shift;

                unsigned weight;

                fg[0] = 
                fg[1] = 
                fg[2] = image_subpixel_scale * image_subpixel_scale / 2;

                x_hr &= image_subpixel_mask;
                y_hr &= image_subpixel_mask;

                fg_ptr = (const value_type*)base_type::source().span(x_lr, y_lr, 2);
                weight = (image_subpixel_scale - x_hr) * 
                         (image_subpixel_scale - y_hr);
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_x();
                weight = x_hr * (image_subpixel_scale - y_hr);
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_y();
                weight = (image_subpixel_scale - x_hr) * y_hr;
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_x();
                weight = x_hr * y_hr;
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                span->r = value_type(fg[order_type::R] >> (image_subpixel_shift * 2));
                span->g = value_type(fg[order_type::G] >> (image_subpixel_shift * 2));
                span->b = value_type(fg[order_type::B] >> (image_subpixel_shift * 2));
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();

            } while(--len);
        }
    };



    //=====================================span_image_filter_rgb_bilinear_clip
    template<class Source, class Interpolator> 
    class span_image_filter_rgb_bilinear_clip : 
    public span_image_filter<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_filter<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::calc_type calc_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask
        };

        //--------------------------------------------------------------------
        span_image_filter_rgb_bilinear_clip() {}
        span_image_filter_rgb_bilinear_clip(source_type& src, 
                                            const color_type& back_color,
                                            interpolator_type& inter) :
            base_type(src, inter, 0),
            m_back_color(back_color)
        {}
        const color_type& background_color() const { return m_back_color; }
        void background_color(const color_type& v)   { m_back_color = v; }

        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);
            calc_type fg[3];
            calc_type src_alpha;
            value_type back_r = m_back_color.r;
            value_type back_g = m_back_color.g;
            value_type back_b = m_back_color.b;
            value_type back_a = m_back_color.a;

            const value_type *fg_ptr;

            int maxx = base_type::source().width() - 1;
            int maxy = base_type::source().height() - 1;

            do
            {
                int x_hr;
                int y_hr;
                
                base_type::interpolator().coordinates(&x_hr, &y_hr);

                x_hr -= base_type::filter_dx_int();
                y_hr -= base_type::filter_dy_int();

                int x_lr = x_hr >> image_subpixel_shift;
                int y_lr = y_hr >> image_subpixel_shift;
                unsigned weight;

                if(x_lr >= 0    && y_lr >= 0 &&
                   x_lr <  maxx && y_lr <  maxy) 
                {
                    fg[0] = 
                    fg[1] = 
                    fg[2] = image_subpixel_scale * image_subpixel_scale / 2;

                    x_hr &= image_subpixel_mask;
                    y_hr &= image_subpixel_mask;

                    fg_ptr = (const value_type*)
                        base_type::source().row_ptr(y_lr) + x_lr + x_lr + x_lr;

                    weight = (image_subpixel_scale - x_hr) * 
                             (image_subpixel_scale - y_hr);
                    fg[0] += weight * *fg_ptr++;
                    fg[1] += weight * *fg_ptr++;
                    fg[2] += weight * *fg_ptr++;

                    weight = x_hr * (image_subpixel_scale - y_hr);
                    fg[0] += weight * *fg_ptr++;
                    fg[1] += weight * *fg_ptr++;
                    fg[2] += weight * *fg_ptr++;

                    ++y_lr;
                    fg_ptr = (const value_type*)
                        base_type::source().row_ptr(y_lr) + x_lr + x_lr + x_lr;

                    weight = (image_subpixel_scale - x_hr) * y_hr;
                    fg[0] += weight * *fg_ptr++;
                    fg[1] += weight * *fg_ptr++;
                    fg[2] += weight * *fg_ptr++;

                    weight = x_hr * y_hr;
                    fg[0] += weight * *fg_ptr++;
                    fg[1] += weight * *fg_ptr++;
                    fg[2] += weight * *fg_ptr++;

                    fg[0] >>= image_subpixel_shift * 2;
                    fg[1] >>= image_subpixel_shift * 2;
                    fg[2] >>= image_subpixel_shift * 2;
                    src_alpha = base_mask;
                }
                else
                {
                    if(x_lr < -1   || y_lr < -1 ||
                       x_lr > maxx || y_lr > maxy)
                    {
                        fg[order_type::R] = back_r;
                        fg[order_type::G] = back_g;
                        fg[order_type::B] = back_b;
                        src_alpha         = back_a;
                    }
                    else
                    {
                        fg[0] = 
                        fg[1] = 
                        fg[2] = 
                        src_alpha = image_subpixel_scale * image_subpixel_scale / 2;

                        x_hr &= image_subpixel_mask;
                        y_hr &= image_subpixel_mask;

                        weight = (image_subpixel_scale - x_hr) * 
                                 (image_subpixel_scale - y_hr);
                        if(x_lr >= 0    && y_lr >= 0 &&
                           x_lr <= maxx && y_lr <= maxy)
                        {
                            fg_ptr = (const value_type*)
                                base_type::source().row_ptr(y_lr) + x_lr + x_lr + x_lr;

                            fg[0] += weight * *fg_ptr++;
                            fg[1] += weight * *fg_ptr++;
                            fg[2] += weight * *fg_ptr++;
                            src_alpha += weight * base_mask;
                        }
                        else
                        {
                            fg[order_type::R] += back_r * weight;
                            fg[order_type::G] += back_g * weight;
                            fg[order_type::B] += back_b * weight;
                            src_alpha         += back_a * weight;
                        }

                        x_lr++;

                        weight = x_hr * (image_subpixel_scale - y_hr);
                        if(x_lr >= 0    && y_lr >= 0 &&
                           x_lr <= maxx && y_lr <= maxy)
                        {
                            fg_ptr = (const value_type*)
                                base_type::source().row_ptr(y_lr) + x_lr + x_lr + x_lr;

                            fg[0]     += weight * *fg_ptr++;
                            fg[1]     += weight * *fg_ptr++;
                            fg[2]     += weight * *fg_ptr++;
                            src_alpha += weight * base_mask;
                        }
                        else
                        {
                            fg[order_type::R] += back_r * weight;
                            fg[order_type::G] += back_g * weight;
                            fg[order_type::B] += back_b * weight;
                            src_alpha         += back_a * weight;
                        }

                        x_lr--;
                        y_lr++;

                        weight = (image_subpixel_scale - x_hr) * y_hr;
                        if(x_lr >= 0    && y_lr >= 0 &&
                           x_lr <= maxx && y_lr <= maxy)
                        {
                            fg_ptr = (const value_type*)
                                base_type::source().row_ptr(y_lr) + x_lr + x_lr + x_lr;

                            fg[0] += weight * *fg_ptr++;
                            fg[1] += weight * *fg_ptr++;
                            fg[2] += weight * *fg_ptr++;
                            src_alpha += weight * base_mask;
                        }
                        else
                        {
                            fg[order_type::R] += back_r * weight;
                            fg[order_type::G] += back_g * weight;
                            fg[order_type::B] += back_b * weight;
                            src_alpha         += back_a * weight;
                        }

                        x_lr++;

                        weight = x_hr * y_hr;
                        if(x_lr >= 0    && y_lr >= 0 &&
                           x_lr <= maxx && y_lr <= maxy)
                        {
                            fg_ptr = (const value_type*)
                                base_type::source().row_ptr(y_lr) + x_lr + x_lr + x_lr;

                            fg[0] += weight * *fg_ptr++;
                            fg[1] += weight * *fg_ptr++;
                            fg[2] += weight * *fg_ptr++;
                            src_alpha += weight * base_mask;
                        }
                        else
                        {
                            fg[order_type::R] += back_r * weight;
                            fg[order_type::G] += back_g * weight;
                            fg[order_type::B] += back_b * weight;
                            src_alpha         += back_a * weight;
                        }

                        fg[0] >>= image_subpixel_shift * 2;
                        fg[1] >>= image_subpixel_shift * 2;
                        fg[2] >>= image_subpixel_shift * 2;
                        src_alpha >>= image_subpixel_shift * 2;
                    }
                }

                span->r = (value_type)fg[order_type::R];
                span->g = (value_type)fg[order_type::G];
                span->b = (value_type)fg[order_type::B];
                span->a = (value_type)src_alpha;
                ++span;
                ++base_type::interpolator();

            } while(--len);
        }
    private:
        color_type m_back_color;
    };



    //===============================================span_image_filter_rgb_2x2
    template<class Source, class Interpolator> 
    class span_image_filter_rgb_2x2 : 
    public span_image_filter<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_filter<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::calc_type calc_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask
        };

        //--------------------------------------------------------------------
        span_image_filter_rgb_2x2() {}
        span_image_filter_rgb_2x2(source_type& src, 
                                  interpolator_type& inter,
                                  const image_filter_lut& filter) :
            base_type(src, inter, &filter) 
        {}


        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);

            calc_type fg[3];

            const value_type *fg_ptr;
            const int16* weight_array = base_type::filter().weight_array() + 
                                        ((base_type::filter().diameter()/2 - 1) << 
                                          image_subpixel_shift);
            do
            {
                int x_hr;
                int y_hr;

                base_type::interpolator().coordinates(&x_hr, &y_hr);

                x_hr -= base_type::filter_dx_int();
                y_hr -= base_type::filter_dy_int();

                int x_lr = x_hr >> image_subpixel_shift;
                int y_lr = y_hr >> image_subpixel_shift;

                unsigned weight;
                fg[0] = fg[1] = fg[2] = image_filter_scale / 2;

                x_hr &= image_subpixel_mask;
                y_hr &= image_subpixel_mask;

                fg_ptr = (const value_type*)base_type::source().span(x_lr, y_lr, 2);
                weight = (weight_array[x_hr + image_subpixel_scale] * 
                          weight_array[y_hr + image_subpixel_scale] + 
                          image_filter_scale / 2) >> 
                          image_filter_shift;
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_x();
                weight = (weight_array[x_hr] * 
                          weight_array[y_hr + image_subpixel_scale] + 
                          image_filter_scale / 2) >> 
                          image_filter_shift;
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_y();
                weight = (weight_array[x_hr + image_subpixel_scale] * 
                          weight_array[y_hr] + 
                          image_filter_scale / 2) >> 
                          image_filter_shift;
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg_ptr = (const value_type*)base_type::source().next_x();
                weight = (weight_array[x_hr] * 
                          weight_array[y_hr] + 
                          image_filter_scale / 2) >> 
                          image_filter_shift;
                fg[0] += weight * *fg_ptr++;
                fg[1] += weight * *fg_ptr++;
                fg[2] += weight * *fg_ptr;

                fg[0] >>= image_filter_shift;
                fg[1] >>= image_filter_shift;
                fg[2] >>= image_filter_shift;

                if(fg[order_type::R] > base_mask) fg[order_type::R] = base_mask;
                if(fg[order_type::G] > base_mask) fg[order_type::G] = base_mask;
                if(fg[order_type::B] > base_mask) fg[order_type::B] = base_mask;

                span->r = (value_type)fg[order_type::R];
                span->g = (value_type)fg[order_type::G];
                span->b = (value_type)fg[order_type::B];
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();

            } while(--len);
        }
    };



    //===================================================span_image_filter_rgb
    template<class Source, class Interpolator> 
    class span_image_filter_rgb : 
    public span_image_filter<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_filter<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::calc_type calc_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask
        };

        //--------------------------------------------------------------------
        span_image_filter_rgb() {}
        span_image_filter_rgb(source_type& src, 
                              interpolator_type& inter,
                              const image_filter_lut& filter) :
            base_type(src, inter, &filter) 
        {}

        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);

            int fg[3];
            const value_type *fg_ptr;

            unsigned     diameter     = base_type::filter().diameter();
            int          start        = base_type::filter().start();
            const int16* weight_array = base_type::filter().weight_array();

            int x_count; 
            int weight_y;

            do
            {
                base_type::interpolator().coordinates(&x, &y);

                x -= base_type::filter_dx_int();
                y -= base_type::filter_dy_int();

                int x_hr = x; 
                int y_hr = y; 

                int x_lr = x_hr >> image_subpixel_shift;
                int y_lr = y_hr >> image_subpixel_shift;

                fg[0] = fg[1] = fg[2] = image_filter_scale / 2;

                int x_fract = x_hr & image_subpixel_mask;
                unsigned y_count = diameter;

                y_hr = image_subpixel_mask - (y_hr & image_subpixel_mask);
                fg_ptr = (const value_type*)base_type::source().span(x_lr + start, 
                                                                     y_lr + start, 
                                                                     diameter);
                for(;;)
                {
                    x_count  = diameter;
                    weight_y = weight_array[y_hr];
                    x_hr = image_subpixel_mask - x_fract;
                    for(;;)
                    {
                        int weight = (weight_y * weight_array[x_hr] + 
                                     image_filter_scale / 2) >> 
                                     image_filter_shift;

                        fg[0] += weight * *fg_ptr++;
                        fg[1] += weight * *fg_ptr++;
                        fg[2] += weight * *fg_ptr;

                        if(--x_count == 0) break;
                        x_hr  += image_subpixel_scale;
                        fg_ptr = (const value_type*)base_type::source().next_x();
                    }

                    if(--y_count == 0) break;
                    y_hr  += image_subpixel_scale;
                    fg_ptr = (const value_type*)base_type::source().next_y();
                }

                fg[0] >>= image_filter_shift;
                fg[1] >>= image_filter_shift;
                fg[2] >>= image_filter_shift;

                if(fg[0] < 0) fg[0] = 0;
                if(fg[1] < 0) fg[1] = 0;
                if(fg[2] < 0) fg[2] = 0;

                if(fg[order_type::R] > base_mask) fg[order_type::R] = base_mask;
                if(fg[order_type::G] > base_mask) fg[order_type::G] = base_mask;
                if(fg[order_type::B] > base_mask) fg[order_type::B] = base_mask;

                span->r = (value_type)fg[order_type::R];
                span->g = (value_type)fg[order_type::G];
                span->b = (value_type)fg[order_type::B];
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();

            } while(--len);
        }
    };



    //==========================================span_image_resample_rgb_affine
    template<class Source> 
    class span_image_resample_rgb_affine : 
    public span_image_resample_affine<Source>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef span_image_resample_affine<source_type> base_type;
        typedef typename base_type::interpolator_type interpolator_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::long_type long_type;
        enum base_scale_e
        {
            base_shift      = color_type::base_shift,
            base_mask       = color_type::base_mask,
            downscale_shift = image_filter_shift
        };

        //--------------------------------------------------------------------
        span_image_resample_rgb_affine() {}
        span_image_resample_rgb_affine(source_type& src, 
                                       interpolator_type& inter,
                                       const image_filter_lut& filter) :
            base_type(src, inter, filter) 
        {}


        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);

            long_type fg[3];

            int diameter     = base_type::filter().diameter();
            int filter_scale = diameter << image_subpixel_shift;
            int radius_x     = (diameter * base_type::m_rx) >> 1;
            int radius_y     = (diameter * base_type::m_ry) >> 1;
            int len_x_lr     = 
                (diameter * base_type::m_rx + image_subpixel_mask) >> 
                    image_subpixel_shift;

            const int16* weight_array = base_type::filter().weight_array();

            do
            {
                base_type::interpolator().coordinates(&x, &y);

                x += base_type::filter_dx_int() - radius_x;
                y += base_type::filter_dy_int() - radius_y;

                fg[0] = fg[1] = fg[2] = image_filter_scale / 2;

                int y_lr = y >> image_subpixel_shift;
                int y_hr = ((image_subpixel_mask - (y & image_subpixel_mask)) * 
                                base_type::m_ry_inv) >> 
                                    image_subpixel_shift;
                int total_weight = 0;
                int x_lr = x >> image_subpixel_shift;
                int x_hr = ((image_subpixel_mask - (x & image_subpixel_mask)) * 
                                base_type::m_rx_inv) >> 
                                    image_subpixel_shift;

                int x_hr2 = x_hr;
                const value_type* fg_ptr = 
                    (const value_type*)base_type::source().span(x_lr, y_lr, len_x_lr);
                for(;;)
                {
                    int weight_y = weight_array[y_hr];
                    x_hr = x_hr2;
                    for(;;)
                    {
                        int weight = (weight_y * weight_array[x_hr] + 
                                     image_filter_scale / 2) >> 
                                     downscale_shift;

                        fg[0] += *fg_ptr++ * weight;
                        fg[1] += *fg_ptr++ * weight;
                        fg[2] += *fg_ptr   * weight;
                        total_weight += weight;
                        x_hr  += base_type::m_rx_inv;
                        if(x_hr >= filter_scale) break;
                        fg_ptr = (const value_type*)base_type::source().next_x();
                    }
                    y_hr += base_type::m_ry_inv;
                    if(y_hr >= filter_scale) break;
                    fg_ptr = (const value_type*)base_type::source().next_y();
                }

                fg[0] /= total_weight;
                fg[1] /= total_weight;
                fg[2] /= total_weight;

                if(fg[0] < 0) fg[0] = 0;
                if(fg[1] < 0) fg[1] = 0;
                if(fg[2] < 0) fg[2] = 0;

                if(fg[order_type::R] > base_mask) fg[order_type::R] = base_mask;
                if(fg[order_type::G] > base_mask) fg[order_type::G] = base_mask;
                if(fg[order_type::B] > base_mask) fg[order_type::B] = base_mask;

                span->r = (value_type)fg[order_type::R];
                span->g = (value_type)fg[order_type::G];
                span->b = (value_type)fg[order_type::B];
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();
            } while(--len);
        }
    };



    //=================================================span_image_resample_rgb
    template<class Source, class Interpolator>
    class span_image_resample_rgb : 
    public span_image_resample<Source, Interpolator>
    {
    public:
        typedef Source source_type;
        typedef typename source_type::color_type color_type;
        typedef typename source_type::order_type order_type;
        typedef Interpolator interpolator_type;
        typedef span_image_resample<source_type, interpolator_type> base_type;
        typedef typename color_type::value_type value_type;
        typedef typename color_type::long_type long_type;
        enum base_scale_e
        {
            base_shift = color_type::base_shift,
            base_mask  = color_type::base_mask,
            downscale_shift = image_filter_shift
        };

        //--------------------------------------------------------------------
        span_image_resample_rgb() {}
        span_image_resample_rgb(source_type& src, 
                                interpolator_type& inter,
                                const image_filter_lut& filter) :
            base_type(src, inter, filter)
        {}

        //--------------------------------------------------------------------
        void generate(color_type* span, int x, int y, unsigned len)
        {
            base_type::interpolator().begin(x + base_type::filter_dx_dbl(), 
                                            y + base_type::filter_dy_dbl(), len);
            long_type fg[3];

            int diameter = base_type::filter().diameter();
            int filter_scale = diameter << image_subpixel_shift;

            const int16* weight_array = base_type::filter().weight_array();
            do
            {
                int rx;
                int ry;
                int rx_inv = image_subpixel_scale;
                int ry_inv = image_subpixel_scale;
                base_type::interpolator().coordinates(&x,  &y);
                base_type::interpolator().local_scale(&rx, &ry);
                base_type::adjust_scale(&rx, &ry);

                rx_inv = image_subpixel_scale * image_subpixel_scale / rx;
                ry_inv = image_subpixel_scale * image_subpixel_scale / ry;

                int radius_x = (diameter * rx) >> 1;
                int radius_y = (diameter * ry) >> 1;
                int len_x_lr = 
                    (diameter * rx + image_subpixel_mask) >> 
                        image_subpixel_shift;

                x += base_type::filter_dx_int() - radius_x;
                y += base_type::filter_dy_int() - radius_y;

                fg[0] = fg[1] = fg[2] = image_filter_scale / 2;

                int y_lr = y >> image_subpixel_shift;
                int y_hr = ((image_subpixel_mask - (y & image_subpixel_mask)) * 
                               ry_inv) >> 
                                   image_subpixel_shift;
                int total_weight = 0;
                int x_lr = x >> image_subpixel_shift;
                int x_hr = ((image_subpixel_mask - (x & image_subpixel_mask)) * 
                               rx_inv) >> 
                                   image_subpixel_shift;
                int x_hr2 = x_hr;
                const value_type* fg_ptr = 
                    (const value_type*)base_type::source().span(x_lr, y_lr, len_x_lr);

                for(;;)
                {
                    int weight_y = weight_array[y_hr];
                    x_hr = x_hr2;
                    for(;;)
                    {
                        int weight = (weight_y * weight_array[x_hr] + 
                                     image_filter_scale / 2) >> 
                                     downscale_shift;
                        fg[0] += *fg_ptr++ * weight;
                        fg[1] += *fg_ptr++ * weight;
                        fg[2] += *fg_ptr   * weight;
                        total_weight += weight;
                        x_hr  += rx_inv;
                        if(x_hr >= filter_scale) break;
                        fg_ptr = (const value_type*)base_type::source().next_x();
                    }
                    y_hr += ry_inv;
                    if(y_hr >= filter_scale) break;
                    fg_ptr = (const value_type*)base_type::source().next_y();
                }

                fg[0] /= total_weight;
                fg[1] /= total_weight;
                fg[2] /= total_weight;

                if(fg[0] < 0) fg[0] = 0;
                if(fg[1] < 0) fg[1] = 0;
                if(fg[2] < 0) fg[2] = 0;

                if(fg[order_type::R] > base_mask) fg[order_type::R] = base_mask;
                if(fg[order_type::G] > base_mask) fg[order_type::G] = base_mask;
                if(fg[order_type::B] > base_mask) fg[order_type::B] = base_mask;

                span->r = (value_type)fg[order_type::R];
                span->g = (value_type)fg[order_type::G];
                span->b = (value_type)fg[order_type::B];
                span->a = base_mask;

                ++span;
                ++base_type::interpolator();
            } while(--len);
        }
    };


}


#endif